Conventionally, compressors equipped with some types of compressing mechanisms, such as a scroll type and a swing type, have been used for refrigeration devices performing refrigeration cycle, such as an air conditioner.
In such compressors, as shown in Laid-Open Japanese Patent Publication No. 9-79153, a scroll-type compressing mechanism and a motor are disposed in a sealed casing, and the compressing mechanism is coupled to the motor by a drive shaft.
Further, a bearing for the drive shaft is provided between the compressing mechanism and the motor. A suction pipe is coupled to the compressing mechanism, while a discharge pipe is coupled to the casing. The discharge pipe is disposed close to the bearing.
In the compressor, the drive shaft and the bearing constitute a journal bearing. As shown in FIG. 8, a conventional journal bearing (101) comprises a drive shaft (103) and a bearing (105) through which the drive shaft (103) passes, while an oil supply passage (107) is formed in the drive shaft (103). Lubricating oil from the oil supply passage (107) through a branch passage (109) is supplied to a gap between an outer peripheral surface of the drive shaft (103) and an inner peripheral surface of the bearing (105).
The lubricating oil supplied to the gap between the drive shaft (103) and the bearing (105) generates an oil-film pressure by wedge effect, and this oil-film pressure enables the drive shaft (103) to be supported by the bearing (105) so as to rotate therein. A distribution of the oil-film pressure in the axis direction shows its characteristics shown in FIG. 9. Namely, because both of upper and lower end surfaces (111, 113) of the bearing (105) are affected by atmospheric pressure, it has the greatest oil-film pressure at its central portion in the axis direction and the pressure gradually decreases toward the both ends, having a mountain-like shape. As a result, the lubricating oil supplied to the gap between the outer peripheral surface of the drive shaft (103) and the inner peripheral surface of the bearing (105) is discharged from the both of upper and lower end surfaces (111, 113) of the bearing (105).
The lubricating oil provided at the journal bearing (101) plays important roles of not only supporting a load, but also cooling a friction heat caused by the drive shaft (103) and the bearing (105).
Problems to Be Solved
The conventional journal bearing (101) in the above-described compressor is just so constituted that lubricating oil merely flows out of the both of upper and lower end surfaces (111, 113) of the bearing (105), without taking any measures against the flowing-out of lubricating oil.
Accordingly, there was a problem that when the lubricating oil flows out of the lower end surface (113) of the bearing (105), the lubricating oil flows into and down the discharge pipe along with a coolant flowing in the discharge pipe. Because the discharge pipe is disposed such that it opens close to the journal bearing (101). Thus, this leakage of lubricating oil caused a problem that the compressor may be lack of lubricating oil.
Herein, some measures to restrict the lubricating oil flowing out can be considered, such as reducing the amount of lubricating oil supplied to a bearing portion (115) constituted of the outer peripheral surface of the drive shaft (103) and the inner peripheral surface of the bearing (105), and sealing the both ends of the bearing portion (115) by sealing materials.
However, in the measures of reducing the supply amount of lubricating oil, the function of supporting the drive shaft (103) may deteriorate, and the cooling effect by lubricating oil may decrease. On the other hand, in the measures by the sealing materials, the cooling effect by lubricating oil may deteriorate due to stagnation of the lubricating oil at the bearing portion (115). Thus, either of measures may cause other problems.
The present invention has been devised in view of the above-described problems, and an object of the present invention is to suppress such leakage of lubricating oil by suppressing the lubricating oil flowing out of at least one end of the bearing.